WATERSHED MANAGEMENT - INTRODUCTION

INTRODUCTION
(WATERSHED MANAGEMENT)
UNIT–I

What is Watershed?
A watershed is a basin-like landform defined by highpoints and ridgelines
that descend into lower elevations and stream valleys.
In other words, a watershed describes an area of land that contains a
common set of streams and rivers that all drain into a single larger body of
water, such as a larger river, a lake or an ocean.
A watershed or catchments is defined as any surface (varying from a few
hectares to several thousand square kilometers) in which rainfall is
collected and conveyed to a common natural waterway
"Watershed is a geo-hydrological unit draining run-off water at a common
point and it could be demarcated based on ridge and gully lines".

Streams
Ridgeline
Common Point
Watershed can be defined as a geo-hydrological unit draining to
a common point by a system of drains. All lands on earth are
part of one watershed or other. Watershed is thus the land and
water area, which contributes runoff to a common point.

 AQUIFERS : Layers of earth that contain water
 CONDENSES : Changes from a gas to a liquid
 EVAPORATION : Changes from a liquid to a gas
 EVAPOTRANSPIRATION: The transfer of water to the
atmosphere by evaporation from
the soil and transpiration by land
plants
 GROUND WATER : Water contained within an aquifer, i.e.
soil or rock
 HYDROLOGIC CYCLE : The earth’s water cycle – movement
of water from the atmosphere to
the earth, its distribution on the
earth and its return to the
atmosphere
 IMPERVIOUS : A material that water cannot pass
through
 INFILTRATION : Water seeping into the ground
 PERMEABILITY : The ease with which water

 PRECIPITATION : Moisture deposited on the earth as
dew, rain or snow
 RUNOFF : Water that travels across the land
surface to rivers, lakes and the
ocean
 SATURATED : Unable to hold any more water
 TRANSPIRATION : The process by which liquid water
taken into a plant from the
soils is released to the
atmosphere as a gas
 WATER TABLE : The top of the water surface in
the saturated part of an aquifer

WATERSHED DEVELOPMENT IN INDIA:

 Is the process of managing human activities and natural
resources on a watershed basis, taking into account, social,
economic and environmental issues, as well as community
interests in order to manage water resources sustainably.
Integrated Watershed Management Provides Multiple
Benefits:
 Through integrated watershed management (IWM), all
community interests work together to identify what issues and
actions are impacting the watershed’s resources, and then
map out different strategies and plans to address those
issues. These plans and strategies are implemented,
monitored, reported on, and updated —on a regular basis—
in order to adapt to changing land uses, new or increasing
stressors, new information, IWM helps us to focus on
priorities and link strategies and actions leading to smarter,
science-based decisions that ensure a long and healthy
future.
Integrated & Multi Disciplinary
Approach

An Integrated Watershed Management approach would
support:
•Improved water quality & quantity
•Flood and erosion management,
•Resilient biodiversity and habitats,
•Sustainable economic and recreation opportunities,
•Improved quality of life and neighborhood desirability,
•Greater ability for Ontario’s watersheds to adapt to the impacts
of climate change, urbanization and other stressors.

“Community watersheds are growth engines for the development of
dry land areas. Since the beginning of watershed programs, the
approach is constantly evolving in India. Today watershed projects
do not focus on water conservation solely; integrated watershed
management plays an important role in ensuring food security,
reducing poverty, protecting the environment and addressing
issues such as equity and improved livelihoods.”
Watershed approach invites integrated inputs of various disciplines for the
developments of different minor watersheds or sub-order streams and streamlets
in accordance with their characteristics. The approach may be key to:

Protect natural resources
Attain good yields
Coordinate the manpower with limited funds
Community participation
As such, the technical status of the conditions, their present trend,
and resources potential form foundation for integrated approach.
The approach may be broadly outlined as assessing multi-
disciplinary overview for appreciating the conditions and trends
with a view to achieve holistic management of the resources for
maximum productivity while preserving the environment with the
funds available.

CHARACTERISTICSOF WATERSHED
IMPORTANT CHARACTERISTICS:
1. SIZE
2. SHAPE
3. PHYSIOGRAPHY
4. SLOPE
5. CLIMATE
6. DRAINAGE
7. LAND USE
8. VEGETATION
9. GEOLOGY AND SOILS
10. HYDROLOGY
11. HYDROGEOLOGY
12. SOCIO ECONOMICS

1. SIZE:
 Size of watershed determines the quantity of rainfall received
retained and disposed off (Runoff). Larger the watershed,
larger is the channel and storage of water in basin. Large
watershed characteristics are topography, geology, soil,
climate and land use and vegetation.
2. SHAPE:
 Watershed may have several shapes like, square, triangle,
rectangular, oval, palm, fern leaf shape etc. Shape of
watershed determines the shape index.
{Farm Factor (FP) =Wb / Lb}
Wb = Width of basin
Lb = Travel time of water through a watershed
 That is the length: width ratio which in turn has a great effect
on runoff disposal. Larger the watershed, higher is the time of
concentration and more water will infiltrate, evaporate or get
utilized by the vegetation. Reverse is the situation when
watershed is shorter in length as compared to width.

3. PHYSIOGRAPHY:
 Type of land, its altitude and physical disposition immensely
speak about a watershed as to the climate and planning the
activities in greening.
For ex: - A hilly track could be useful mainly for forestry and
plains of populated areas could be utilized only for crops.
4. SLOPE:
 It controls the rainfall distribution and movement, land
utilization and watershed behavior. The degree of slope
affects the velocity of overland flow and runoff, infiltration rate
and thus soil transportation.
5. CLIMATE:
 Meteorological parameters like precipitation, temperature,
wind velocity, humidity and evaporation decide a quantitative
approach for arriving at water availability in a watershed.
Climate is a determining factor for the management of all
aspects of watershed.
For ex: - The entire planning of greenery depends on

 Climate parameters affect watershed functioning and its
manipulation in two ways.
A. Rain provides incoming precipitation along with its various
characteristic like intensity, frequency and amount of rainfall.
B. Parameters like rainfall, temperature, humidity, wind
velocity, etc. regulates factors like soil and vegetation.
6. DRAINAGE:
 The order, pattern and density of drainage have a profound
influence on watershed as to runoff, infiltration, land
management etc. It determines the flow characteristics and
thus erosional behavior.
 Topography regulates drainage. Drainage density [length of
all drainage channels – unit area], length, width depth of main
and subsidiary channel, main outlet and its size depend on
photography. Drainage pattern affect time of concentration.

7. LAND USE:
 Land use pattern is vital for planning, programming and
implementing a management project on a watershed. It is an
important statistic for ascertaining the background, appreciating
the status and planning the programs in management. It portrays
man’s impact on the specific watershed and forms a basis for
categorizing the land for the formulation of a pragmatically action
plan.
 Type of land use, its extent and management are the key factors
which affect watershed behavior. Judicious land use by users
[human beings] is of vital importance to watershed management
and functioning.
8. VEGETATION:
 Detailed information on vegetation helps in choosing type,
mode and manner of greening the watershed. Information on
local species gives a sure ground for selecting plants and
crops. It confirms authoritatively what greenery can be grown
where, with care, soil capabilities could be analyzed,
compared and profitably confirmed for management.
 Depending upon the type of vegetation and its extent, this
factor regulates the functioning of watershed
 For ex: - Infiltration, water retention, runoff production,

9. GEOLOGY AND SOILS:
 Rocks and their structure control the formation of a watershed
itself because their nature determines size, shape,
physiography, drainage and ground water conditions. Soils,
derivative of rock, are basic to greening. Soil parameters as to
depth, nature, moisture and fertility determine crops. Rocks and
soils, together influence water storage, movement and
infiltration.
 Geological formation and rock types affect extent of water
erosion, erodibility of channels and hill faces, sediment
production. Rocks like shale’s, phyllites erode easily where as
igneous rocks do not erode.
 Physical and chemical properties of soil, specially texture, and
structure and soil depth influence disposition of water by way of
infiltration, storage and runoff.
10. HYDROLOGY:
 Availability, quality and distribution of surface water is basic to
the final goal of growing greenery in a watershed. Hydrological
parameters help in quantification of water available, utilized and

11. HYDROGEOLOGY:
 The demand for ground water is ever on the increase, as
such the appreciation of ground water resources for
determining their further availability in the context of
conjunctive use of water resources for greening the specific
watershed is a logical prelude.
 The information should not only include nature, thickness and
characteristics of aquifers but also contain quantity available
for additional exploitation through specific number of wells.
12. SOCIO – ECONOMICS:
 Statistics on people and their health, hygiene, wealth, wants,
wishes, cattle and farming practices and share of participation
are equally important in managing a watershed.

WATERSHED CHARACTERISTICS
•Bio physical and socio economic features prevalent in a
watershed
•It’s need to be identified for management and planning of
watershed
Watershed can be broadly categorized into:
a. Climate
b. Geology and Physiography
c. Soils
d. Land use and cover conditions
e. Watershed hydrology
f. Socio- Economic features in watershed

a. Climate:
Precipitation
Evaporation
Wind
Relative humidity etc.,
b. Physiography:
Size and Shape of watershed
Elevation
Slope and aspect
 Geology:
Drainage features (Pattern, Density, etc.,)
Parent rock types (Igneous, Sedimentary, etc.,)
c. Soils:
Soil Depth
Soil Type
Soil Infiltration capacity
Soil Erosiveness etc.,

d. Land Use and Cover Condition:
Land use types (Forest, Grass land, Agriculture, Urban,
etc.,)
Ownership pattern (Govt., Private, Industrial)
Agricultural Practices
Recreational use (Resort, Wild life, Fish resources etc.,)
e. Watershed Hydrology:
Erosion conditions along streams
Floods
Stream flow (Quantity and Quality)
f. Socio – Economic features / Watershed Use:
Water use and needs (Source of water, Domestic use,
Irrigation, Industrial, Power generation etc.,)
Water use problems (Erosion, Flooding, Siltation, Water
supply, Water quality etc.,)
Income generation activities associated with Watershed
Management

 Topography:
 Slope, length, degree and uniformity of slope affect both
disposal of water and soil loss. Degree and length of slope
also affect time of concentration [TC] and infiltration of water.
 Drainage: Topography regulates drainage. Drainage density
[length of all drainage channels – unit area], length, width
depth of main and subsidiary channel, main outlet and its size
depend on photography. Drainage pattern affect time of
concentration.
 Drainage area {A}:
 Most important for hydrologic design
 Reflects volume of water
 Generated from rainfall
 The volume of water available for runoff may be assumed as
product of rainfall depth & drainage area
 Drainage area input to all models.

BASIC DATA ON WATERSHEDS
Proforma for basic data on Watersheds:

Sl. No Feature No / Quantity
1 Milch Animals
Cows
Buffaloes
Goats
Sheep’s
2 Draught Animals
Ox
He Buffalo
3 Others
Poultry
- Back Yard
-Commercial
Piggery
Live Stock Details:

Sl. No Feature No / Quantity
4
Total Milk Production from Milch
Animals ( Liters / Day)
Cows
She Buffaloes
5 Fodder Availability
Existing Area under green fodder (Ha)
Dry Fodder ( Tons / Year)
No. of silage pits
6 Supplementary feed ( Kg / day)
7 Fuel Wood Availability
Existing Area under Fuel wood (Ha)

WATERSHED MANAGEMENT - INTRODUCTION

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